Operation of electric motors often requires a dedicated controller. The controller may need to determine the position of the rotor in order to control the electric motor. Some controllers may determine the position of the rotor without sensors. For example, a controller may determine the position of the rotor count using a technique known as ripple counting, which includes counting the number of ripples in the current caused by the back electromagnetic force (BEMF) and the commutation of the rotor. The controller may determine the position of the rotor based on the ripple count. In some examples, a controller may control the rotor using pulse-width modulation (PWM). If the frequency of the PWM signal is similar to the frequency of the ripples caused by the commutation, the controller may not be able to accurately count the number of ripples in the current.